Recently, many copying machines are combined with automatic document feeders and sheet post-processing apparatuses for stapling or punching the copied sheets in order to automate the process. The automatic document feeder is placed on a document tray of the copying machine, for example, for transporting a plurality of documents one by one onto the document tray of the copying machine. The sheet post-processing apparatus is provided for carrying out a post-process of sheets, such as stapling, punching, etc., on every predetermined number of sheets with images on documents copied thereto fed from the copying machine.
An example of the conventional sheet post-processing apparatus is shown in FIG. 33. The apparatus is provided with separately provided three transport paths: a transport path 101 for transporting sheets from a copying machine main body (not shown), a non-processing discharge path 102 for transporting non-processed sheets transported through the transport path 101, and a processing discharge path 103 for discharging processed sheets fed through the transport path 101. At the respective discharge ends of the discharge paths 102 and 103, provided are a non-processed sheet discharge opening 102a and a processed set discharge opening 103a.
In the described apparatus, when for example an offset mode (non-processing mode) is selected by the copying machine main body, the sheets transported from the main body are fed into the transport path 101, and further transported into the non-processing discharge path 102 by transport rollers 113 via a deflector 105 which is rotated beforehand in a X direction shown by an arrow. Then, sheets are discharged through the non-processing sheet discharge opening 102a by discharge rollers 110 onto a discharge tray 106 which is inclined at a predetermined angle. The sheets discharged onto the discharge tray 106 are aligned by rotating a aligning roller 111 which pushes the sheets until the trailing edges thereof come in contact with an aligner plate 112.
On the other hand, when, for example, a staple mode (processing mode) is selected in the copying machine main body, the sheets transported from the main body are first fed into the transport path 101, and further transported into the processing discharge path 103 by the transport rollers 113 via the deflector 105 rotated beforehand in a Y direction shown by an arrow so as to place the sheets onto a processing tray 104. When a predetermined number of sheets are stacked on the processing tray 104, a stapling process is carried out. Then, the processed sheets are discharged onto the discharge tray 106 through the processed set discharge opening 103a by a pushing member 109.
The processing tray 104 is inclined in a direction where the processed set discharge opening 103a is provided on an upper end thereof and a stopper 108 is provided on a lower end thereof. Therefore, in the staple mode, the sheets fed into the processed sheet discharge path 103 from the transport path 101 are temporarily discharged onto the discharge tray 106 through the processed set discharge opening 103a from the leading edges thereof, and after the sheets are completely discharged, the sheets are dropped by the dead weight until the trailing edges thereof are stopped by the stopper 108 provided on the processing tray 104. In this state, the sheets are placed over the discharge tray 106 and the processing tray 104. Additionally, a paddler 107 is provided so as to support the sheets being dropped to the stopper 108 being rotated in a Z direction shown by an arrow.
In the described sheet post-processing apparatus, in the staple mode, the sheets are placed over the discharge tray 106 and the processing tray 104, and in order to accurately process the sheets, it is required to surely drop the sheets to the stopper 108. Moreover, when discharging a complete set from the processing tray 104 onto the discharge tray 106, the complete set become heavy as being composed of a plurality of sheets, thereby presenting the problem that a discharge failure may occur by being buckled in the discharge process due to the dead weight. In order to counteract this, it is preferable that a sheet receiving face 106a of the discharge tray 106 is formed on a plane extended from the surface of the processing tray 104 at the same or almost same angle as shown in FIG. 33.
On the other hand, in the offset mode, as the sheets are discharged onto the discharge tray 106 one by one, the dead weight of the sheet to be discharged is light, and thus the discharge tray 106 must have a greater angle with respect to the horizontal direction than that in the staple mode in order to desirably align the sheets on the discharge tray 106.
As shown in FIG. 34(a), the described discharge tray 106 is arranged such that the sheet receiving face 106 on the side of the aligner plate 112 is inclined. In the offset mode, the trailing edges of the sheets S discharged onto the discharge tray 106 may not be aligned desirably to the aligner plate 112 by rotating the aligning roller 111 as a number of sheets S placed on the discharge tray 106 increases due to the rigidity of the sheets, thereby presenting the problem of lowering the aligning facility of the sheets S.
The discharge tray 116 may be arranged as shown in FIG. 34(b). In this discharge tray 116, since a horizontal section 116b is formed on the side of the aligning roller 111 of the sheet receiving face 116a, the trailing edges of the sheets S can be easily aligned by the aligner plate 112 irrespectively of the rigidity of the sheets S, thereby achieving an improved efficiency of stacking the sheets S onto the discharge tray 106.
However, in this arrangement of the discharge tray 116, when the staple mode is selected, the leading edges of the sheets remain dangling to the horizontal section 116b, and thus it is difficult to precisely drop the sheets to the stopper 108 provided on the stapler plate 104.
Moreover, in both of the discharge trays 106 and 116, as a number of complete sets S increases, the stapled section H of the compete set S becomes more bulky than the non-processed section of the complete set S as shown in FIG. 35. Thus, this raised stapled section H of the complete sheets S may be stuck by contacting the aligning rollers 111 or a shaft 111a or by being creased. Therefore, in the staple mode, a number of sets to be discharged at one time is restricted, thereby presenting the problem of low operation efficiency of the sheet post-processing apparatus.